One example of a motor-driven chair designed particularly for handicapped people is described in a paper dated November 1985 published in Medical and Biological Engineering and Computing by O. Z. Roy et al which relates to an omnidirectional power lab stool.
This device includes a central driven wheel positioned beneath the seat and acting as a main support for the seat. An outrigger frame is positioned around the central wheel and includes a base and turntable on which are mounted four ground wheels spaced around the central wheel. Three of the wheels are castor wheels which are free floating. The fourth wheel is directionally fixed and acts as a rudder for straight-line travel. The base and turntable are rotatable relative to the seat and the central wheel. The central wheel is fixed in direction relative to the seat. The base and turntable are connected to a hoop which surrounds the seat so that the seated occupant is enclosed by the hoop. The hoop is coupled to stand at one side. A drive motor is mounted on the central wheel and extends outwardly from the hub for providing motive power to the drive wheel. A battery mounted on the turntable supplies power to the motor.
This device is simply a prototype proposal and did not achieve any commercial success. It has a number of significant disadvantages. Firstly, the wheel designed is relatively crude and necessitates a bulky motor arrangement coupled on one side of the wheel which interferes with the compact design of the device including the base and turntable arrangement. Secondly the hoop is a major disadvantage in that it is aesthetically very distracting and since it makes it very difficult for even an able bodied user to enter the seat without discomfort. The hoop is however necessary to locate the chair relative to the turntable to prevent multiple rotation of the chair relative to the turntable which would thus twist the wires from the battery to the motor. Furthermore the device is difficult to handle and manouver when there is no occupant.
Further designs of chairs are shown in U.S. Pat. Nos. 4,403,673 (Ball); 4,475,613 (Walker); 3,387,681 (Rabjohn), 3,802,524 (Seidel); and 4,513,832 (Engman). However none of these devices is relevant to the design of the above device or solves any of the difficulties associated with the design.
One of the problems of the above design is the unsatisfactory nature of the wheel and motor construction which is extremelly bulky and thus complicates the construction of the device particularly in the area of the outrigger frame. Attempts have been made to design an arrangement in which the motor for driving the wheel is positioned within the hub of the wheel since this can provide a very compact arrangement particularly suitable for the above design of motorized chair. However a motor-in-the-hub design can also be used in other designs of motorized chair or motorized vehicle with significant advantages of compactness and ease of operation.
Some designs have already been proposed for motor-in-the-hub wheel drive arrangements but these are highly complicated and therefore very costly to manufacture and it is believed that none is commercially successful or has been manufactured on a commercial scale. Various proposals are shown in all U.S. Pat. Nos. 641,603 (Newman); 680,804 (Newman); 1,090,684 (Church); 1,172,456 (Hoadley); 2,608,598 (Hawkins) and more recent U.S. Pat. No. 4,021,690 (Burton). However, as stated above all these devices are highly complicated leading to devices which cannot be manufactured on a commercial scale.